Evidence used
- No CISA KEV confirmation is currently recorded.
- Exploitation requires an existing local or physical foothold with privileges.
- EPSS is 0.11% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2026
CVE-2026-97876High confidence
Bypass of GRUB lockdown restriction in Secure Boot mode via serial command MMIO base address
GNU · grub2
6.4MediumCVSS 3.1
Patch only the product branches with a verified fix
Fix availability varies by productMedium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority. Verified remediation exists for at least one product or source, but 76 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityMedium→Operational priority:Low, lowered one band.downgradedsince 2 Oct 2026
Compensating controls
- Validate the affected product branch and deploy the verified fixed release.
- Restrict local access and enforce least privilege on affected hosts.
- Monitor vendor guidance and exploitation sources for a material change.
Verification
- Confirm that the asset runs GNU grub2 and falls inside the recorded affected range.
- Verify the installed build against the product-specific fixed version after deployment.
- Validate exposure, authentication requirements and compensating controls in the actual environment.
- Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Remediation availability differs by product scope
Verified remediation exists for at least one product or source, but 76 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
- Red Hat Product Security: 75 affected or under-investigation product states without a fixed product state in the same current advisory
- Debian Security Tracker: 1 affected package state with no published fix
Distribution package intelligence
6 package statesRelease-specific package status
Debian, ubuntu findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.
Package result overrides the generic status
BlackTree has verified remediation for at least one product or source, but the relevant distribution still reports no fixed package for 1 affected package state shown here. Treat those rows as affected with no fix until that distribution publishes a fixed version.
Repository candidate not checked
A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.
| Distribution release | Source package | Vendor state | Fixed version | Evidence |
|---|---|---|---|---|
| Debian trixietrixie · source | grub2 | Affected, no fix publishedDebian currently tracks this release as open. | Not published in this feed | Debian Security Tracker ↗Source updated 5 Oct 2026 |
| Debian bookwormbookworm · source | grub2 | Not affectedDebian marks this release not affected (fixed-version marker 0). | Not published in this feed | Debian Security Tracker ↗Source updated 5 Oct 2026 |
| Debian forkyforky · source | grub2 | Vendor fix publishedDebian records a fixed source-package version for this release. | 2.14-4 | Debian Security Tracker ↗Source updated 5 Oct 2026 |
| Debian sidsid · source | grub2 | Vendor fix publishedDebian records a fixed source-package version for this release. | 2.14-4 | Debian Security Tracker ↗Source updated 5 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | grub2-signed | Under evaluationCanonical reports that the package might be affected and still needs evaluation or fixing. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 5 Oct 2026 |
| Ubuntu 24.04 LTSnoble · standard archive | grub2-unsigned | Under evaluationCanonical reports that the package might be affected and still needs evaluation or fixing. | Not published in this feed | Canonical Ubuntu Security ↗Source updated 5 Oct 2026 |
Direct vendor intelligence
1 currentAuthoritative vendor CSAF and VEX advisories
Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.
CVE-2026-97876 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitygrub2: grub2: Secure Boot lockdown bypass via improper serial address validation
The vendor explicitly identifies these products as affected by this CVE.
- grub2-common as a component of Red Hat Enterprise Linux 10
- grub2-efi-aa64 as a component of Red Hat Enterprise Linux 10
- grub2-efi-aa64-cdboot as a component of Red Hat Enterprise Linux 10
- grub2-efi-aa64-modules as a component of Red Hat Enterprise Linux 10
- grub2-efi-x64 as a component of Red Hat Enterprise Linux 10
- grub2-efi-x64-cdboot as a component of Red Hat Enterprise Linux 10
- grub2-efi-x64-modules as a component of Red Hat Enterprise Linux 10
- grub2-pc as a component of Red Hat Enterprise Linux 10
- grub2-pc-modules as a component of Red Hat Enterprise Linux 10
- grub2-ppc64le as a component of Red Hat Enterprise Linux 10
- grub2-ppc64le-modules as a component of Red Hat Enterprise Linux 10
- grub2-tools as a component of Red Hat Enterprise Linux 10
- Summary
- A flaw was found in GRUB2. The bootloader insufficiently validates memory addresses passed to the serial configuration command, allowing arbitrary system memory to be targeted instead of a legitimate serial communication device. A local attacker with control over GRUB's boot configuration can exploit this issue to overwrite internal verification structures. This vulnerability allows the attacker to bypass Secure Boot lockdown restrictions and load arbitrary unsigned modules during system boot.
- Remediation
- Fix deferred
Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority. Verified remediation exists for at least one product or source, but 76 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
Fix availability varies by product01
What, why and how
A local attacker with control over GRUB's configuration can bypass lockdown restrictions when booting with Secure Boot and load an unsigned GRUB module, while GRUB continues to report lockdown is enabled. The vulnerability is caused by insufficient validation of the MMIO base address passed to the GRUB serial command. GRUB does not validate that the base address corresponds to a UART device, rather than being an arbitrary memory address. This allows an attacker to trick GRUB into writing non-arbitrary data at an attacker-controlled address, including resetting the grub_file_verifiers list in a way that disables the subsequent verification of loaded modules.
What
A local attacker with control over GRUB's configuration can bypass lockdown restrictions when booting with Secure Boot and load an unsigned GRUB module, while GRUB continues to report lockdown is enabled. The vulnerability is caused by insufficient validation of the MMIO base address passed to the GRUB serial command. GRUB does not validate that the base address corresponds to a UART device, rather than being an arbitrary memory address. This allows an attacker to trick GRUB into writing non-arbitrary data at an attacker-controlled address, including resetting the grub_file_verifiers list in a way that disables the subsequent verification of loaded modules.
Why
The product obtains a value from an untrusted source, converts this value to a pointer, and dereferences the resulting pointer.
How
An attacker operating through local access may attempt exploitation with elevated privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
What
A local attacker with control over GRUB's configuration can bypass lockdown restrictions when booting with Secure Boot and load an unsigned GRUB module, while GRUB continues to report lockdown is enabled. The vulnerability is caused by insufficient validation of the MMIO base address passed to the GRUB serial command. GRUB does not validate that the base address corresponds to a UART device, rather than being an arbitrary memory address. This allows an attacker to trick GRUB into writing non-arbitrary data at an attacker-controlled address, including resetting the grub_file_verifiers list in a way that disables the subsequent verification of loaded modules.
Why
The product obtains a value from an untrusted source, converts this value to a pointer, and dereferences the resulting pointer.
How
An attacker operating through local access may attempt exploitation with elevated privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
02
Exploit reality and attack path
CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.
Observed exploitation No confirmed evidence
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.
Public PoC / exploit material None recorded
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.
- Likely attack path
- local access → Untrusted Pointer Dereference → cause the confidentiality, integrity or availability impact described by the vendor
- Attack surface
- Local
- Privileges required
- High: elevated access is required
- User interaction
- None
- Attack complexity
- High: exploitation depends on specific conditions
- Security boundary
- Unchanged: impact remains within the vulnerable component's security authority
- Weakness
?
CWE means Common Weakness Enumeration: a standard category for the underlying weakness. - CWE-822 ↗
CWE-822: Untrusted Pointer Dereference. The product obtains a value from an untrusted source, converts this value to a pointer, and dereferences the resulting pointer.
- CVSS vector
?
CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity. CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:HCommon Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVLocalAttack vector: The attacker needs local access to the vulnerable system.ACHighAttack complexity: Successful exploitation depends on specific conditions outside the attacker's direct control.PRHighPrivileges required: The attacker needs elevated or administrative privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.AHighAvailability impact: A successful attack can cause a major loss.- Post-exploitation / living off the land
- The issue can support a local privilege or sandbox boundary transition; normal system utilities may then be available in the gained context.
03
Patch and workaround
Operational remediation based on structured source evidence.
- Status
?
Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change. - Fix availability varies by product
- Affected
- grub2-common as a component of Red Hat Enterprise Linux 10
- grub2-efi-aa64 as a component of Red Hat Enterprise Linux 10
- grub2-efi-aa64-cdboot as a component of Red Hat Enterprise Linux 10
- grub2-efi-aa64-modules as a component of Red Hat Enterprise Linux 10
- grub2-efi-x64 as a component of Red Hat Enterprise Linux 10
- grub2-efi-x64-cdboot as a component of Red Hat Enterprise Linux 10
- grub2-efi-x64-modules as a component of Red Hat Enterprise Linux 10
- grub2-pc as a component of Red Hat Enterprise Linux 10
- grub2-pc-modules as a component of Red Hat Enterprise Linux 10
- grub2-ppc64le as a component of Red Hat Enterprise Linux 10
- grub2-ppc64le-modules as a component of Red Hat Enterprise Linux 10
- grub2-tools as a component of Red Hat Enterprise Linux 10
- grub2-tools-efi as a component of Red Hat Enterprise Linux 10
- grub2-tools-extra as a component of Red Hat Enterprise Linux 10
- grub2-tools-minimal as a component of Red Hat Enterprise Linux 10
- grub2.src as a component of Red Hat Enterprise Linux 10
- grub2 as a component of Red Hat Enterprise Linux 7
- grub2-common as a component of Red Hat Enterprise Linux 7
- grub2-efi as a component of Red Hat Enterprise Linux 7
- grub2-efi-aa64-modules as a component of Red Hat Enterprise Linux 7
- grub2-efi-ia32 as a component of Red Hat Enterprise Linux 7
- grub2-efi-ia32-cdboot as a component of Red Hat Enterprise Linux 7
- grub2-efi-ia32-modules as a component of Red Hat Enterprise Linux 7
- grub2-efi-modules as a component of Red Hat Enterprise Linux 7
- grub2-efi-x64 as a component of Red Hat Enterprise Linux 7
- grub2-efi-x64-cdboot as a component of Red Hat Enterprise Linux 7
- grub2-efi-x64-modules as a component of Red Hat Enterprise Linux 7
- grub2-pc as a component of Red Hat Enterprise Linux 7
- grub2-pc-modules as a component of Red Hat Enterprise Linux 7
- grub2-ppc-modules as a component of Red Hat Enterprise Linux 7
- and 45 more
- Action
- Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
- Workaround
- No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04
Evidence and provenance
Published 2 Oct 2026 · Last source change 2 Oct 2026, 17:45 UTC · CWE-822 · Untrusted Pointer Dereference
CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source FIRST · tracked since 2026-10-03
?
The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.European sourceENISA EUVD · EUVD-2026-91376
Product sourceVendor CSAF · Red Hat Product Security
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD awaiting enrichment
Core structured fields are present and their contributing authorities are shown above.
Material change intelligence
View recent updates ↗What changed after publication
- ENISA EUVD mappingEUVD-2026-91376 was added to the official ENISA EUVD mapping for this CVE.ENISA EUVD ↗
- Before
- not recorded
- After
- {"euvdId":"EUVD-2026-91376"}
- Catalogue recordCVE added to the BlackTree catalogue.CNA ↗
Technical terms and abbreviations used in this report
- CVE
- Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
- CVSS
- Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
- EPSS
- Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
- CWE
- Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
- CNA
- CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
- CISA ADP
- Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
- NVD
- National Vulnerability Database: NIST's enrichment service for CVE records.
- CERT / CSIRT
- A computer security incident response team that publishes warnings or coordinates incident response.
- PoC
- Proof of concept: public material that demonstrates or helps reproduce exploitation.
- CSAF
- Common Security Advisory Framework: a machine-readable format for security advisories.
- LoTL
- Living off the land: abuse of legitimate tools or system functions during an attack.